This is my first post and I would like to know how to compute variables using tangential and normal coordinates. I have results from a 2D fsi collapsable channel and I need to transform the stress tensor from cartesian coordinate system to tangential-normal coordinate system and I don’t know how to do that.

Do you need help with the mathematics or with how to compute the mathematics to arrive at the tangential-normal coordinate system? We can help with the second question here.

In increasing order of difficulty and generality, you can use the Calculator filter, the Python Calculator, or Programmable Filter to carry out the computation. If you supply the math and some details about your dataset, someone may be able to translate that into an expression or script that performs the transformation using one of these filters.